1. Field of the Invention.
The method of the invention has been found to be useful in the field of heat insulation products, although it can be used wherever a liquid binder with a reinforcing fiber must be dispersed through particulate material.
2. Description of the prior art.
Heat insulation products are well known and are widely used in industry. In one form the heat insulation product is used as a preformed unit which encloses pipes carrying hot or cold fluids. Much pipe insulation is used in chemical plants, such as refineries, to conserve energy.
In addition, the heat insulation material may be in the form of blocks or panels which can be secured to the walls of areas requiring heat or cold insulation.
In the past the heat insulation has been made by a molding process in which a slurry of particulate material, such as perlite and liquid inorganic binder is poured into molds and dried to harden the binder.
The slurry has been made by mixing together perlite particles and a liquid inorganic binder in a large rotating drum or vat. To give additional strength to the finished heat insulation products, various fibers have been incorporated into the slurry. The general method of incorporating the fibers has been to mix the particulate matter and the fibers together in dry form and then add the liquid binder. Reference may be had to any of the following patents for details of mixing the particulate matter and the liquid binder:
U.S. Pat. No. 3,367,871 issued on Feb. 6, 1968 to A. P. Mueller and Beverly Asher.
U.S. Pat. No. 3,408,316 issued on Oct. 29, 1968 to the above inventors.
U.S. Pat. No. 3,639,276 issued on Feb. 1, 1972 to the above inventors.
All the above patents are assigned to The Celotex Corporation of Tampa, Florida.
When this method of making the slurry has been followed, there is often a poor distribution of the fibers throughout the slurry. Usually, the fiber dispersion is very nonuniform. Part of the problem starts with the fact that the fibers come in long strands of many filaments. The strands are chopped into shorter lengths and the short lengths of strands are dumped into the mixer with the particulate matter.
In many instances the strands do not break apart into their individual filaments but remain agglomerated even when tumbled with the particulate matter. Thus, for a given number of strands of filaments, the strength imparted to the final heat insulation product is substantially lessened compared to a heat insulation product in which the individual filaments of the strands are uniformly dispersed in the slurry.
The slurry is then poured into molds which are heated to dry the slurry and set the binder to form a molded heat insulation product.